It's worth noting, that libqt4-webkit is no longer a valid package in experimental, but is a transitional package to pull libqtwebkit4, so now QtWebKit and Qt versions are quite independent. You can use Qt 4.6 or 4.7 with the QtWebKit 2.0.

I needed QtWebKit 2.0 on ARM, so I built it from deb-src. It went OK with no modifications of the source package.

When it comes to Qt's 4.7 beta release I needed to patch it slightly, to disable precompiled headers (for some reason, after generating them, they were not found by installation), —fast configure flag (not sure if this is needed) and I needed to tweak src/core/io/io.pri file, because for some reason linux-* {} section of qmake file was not properly applied. Also to properly compile stuff, I added Qt3 support.